旋转机械无线监测中的多普勒效应

Research on Doppler Effect in Wireless Monitoring on Rotating Machinery

由于应用无线通信技术对旋转机械进行状态监测时,无线设备安装在转轴上随轴高速旋转,无线设备之间的相对位置发生变化,因此会产生多普勒效应,影响无线通信。针对这一问题,首先,提出了两种无线设备安装方式;然后,建立了旋转运动中无线设备的多普勒频移理论模型,并分析了影响无线通信的因素;最后,对水润滑轴承水膜压力进行无线监测试验,引入误码率和丢包率研究了其与轴转速之间的关系,并对多普勒频移理论模型进行验证。理论与试验分析结果表明：多普勒频移与无线设备摆动圆直径、轴转速以及电磁波入射角密切相关,尤以转速影响为甚;在433 MHz通信频率下,无线监测方法不能很好地用于转速接近或超过10kr/min的旋转机械;转速对丢包率的影响大于误码率,丢包率为误码率的2~3倍。

In the process of condition monitoring on rotating machinery using a wireless communicationtechnique,the relative positions of pieces of wireless equipment change due to the Doppler effect,which is caused by high speed rotation with the shaft.In this paper,two installation methods of wireless equipment were proposed.Then,the Doppler frequency shift theory model of wireless equipment in rotational motion was established,and the influence factors on wireless communication were analyzed.Finally,the film pressure of a water-lubricated bearing was monitored using a wireless method.The relationship between bit error rate and shaft speed and the relationship between packet loss rate and shaft speed were studied.The Doppler frequency shift theory model was verified.The theoretical and experimental analysis results show that the Doppler frequency shift relates to the swing circle diameter of wireless equipment,the shaft speed,and the incidence angle of the electromagnetic wave,with the shaft speed as the main influential factor.With a communication frequency of 433 MHz,a wireless method cannot be used to monitor rotating machinery whose rotation speed is near or exceeds 10kr/min.The influence of shaft speed on packet loss rate was greater than that on bit error rate,with the packet loss rate being two or three times bigger than the bit error rate.